Electkomagnetic apbon feedeb



. J. P. BETHKE July 12, 1927.

ELECTROMAGNETIC APRON FEEDER 2 sheets-sheet 1 Original Filed March24/1923 INVENTOR.

' ATTORNEY? J. P. BETHKE ELECTROMAGNETIC APRON FEEDER .2 Sheets-Sheet 2July 12, 1927.

ori in l Filed March 24, 1925 M fM A TTORNEYJ Reissued-July 12 1927.

UNITED STATES PATENT OFFICE.

JOHN- P. term, or MILWAUKEE, WISCONSIN,- ASSIGNOR 'ro MAGNETIC MANUFAC-TUBING 00., or MILWAUKEE, WISCONSIN.

ELECTROMAGNETIC APRON FEEDER.

Original No. 1,581,378, dated March 31, 1925, Serial No. 627,297, filedMarch 24, 1923. Application for reissue filed March 25, 1927. Serial No.178,493.

This invention relates to improvements in apron feeders of the generaltype employed for feeding rock, ore, and other materials to crushingmills.

Theobject of this invention is to provide an apron feeder with effectivemeans for separating magnetizable material from the material to becrushed, thereby protecting the crushing mills by removing the harderportions of the material, including fragments of iron and steel brokenor' disengaged from the machinery employed in handling such materials. a

A further object of this invention is to so combine a magnet with anapron feeder as to convert the feeder into an effective magnetic-separator without radical change in structure or design. 1

' A more detailed object is the utilizing of minimum driving power andmagnetic en ergy for attaining maximum efficiency both in the operationof the apron and in ener 'zing the magnetic field exciter while empoying wear-resisting metal in the apron construction, the arrangementand operation of the parts being such as to insure minimum interferenceof the apron with the effectiveness of the magnetic field and of thefield with the operation of the apron.

In the drawings:

Figure 1 is a sectional view of an apron feeder embodying the inventionherein claimed,the section beingtaken on avertical plane which includesthe axis of the sprocket shaft 'at the delivery end of the feeder.

Figure 2 is a sectional viewon line 22 of Figure 1. v

Figure 3 is a view similar to Figure 2, showing an embodiment'of theinvention in which a stationary magnet is utilized.

Figure 4 is a plan view of the magnet or electromagnetic battery shownin Figure 3.

Like parts are identified by the same reference characters throughoutthe several views.

In Figures 1 and 2 the apron is of ordi nary type and comprises asuccession of flat plates or bars 1 having cylindrically curved orarcuate margins 2 and 3 which interlap with the margins of adjacent barsto form an endless belt. At their respective ends the plates 1 aresupported by sprocket chains 4 which travel about end sprocket wheels 5,the connection between the plates and the sprocket chains being madesubstantially 5 along the longitudinal center line of the plates. Thelinks of the sprocket chains have theirv central portions provided witharms 6 for this purpose. But the connecting pins 7 of the links areprovided with rollers. 8 which travel along supporting beams 9. Thespaces between the teeth of the sprocket Wheels are adapted to receivethe rollers 8. The margins 2 and 3 of the apron plates are curved aboutthe axes of the pins 7.

At the delivery end of the conveyor the sprocket wheels 5 are mountedupon a shaft 10 which may serve as the driving shaft, and between thesesprocket wheels an electromagnetic pulley 11' is mounted on the same Ishaft and has a diameter substantially equal tothat of the pitch circleof the sprocket wheels, whereby the periphery of the pulley is broughtinto close proximity to the plates 1 as they pass about the shaft 10without 76 necessarily being in actual contact with the plates. v

The pulley may be of the type disclosed in Letters Patent of the UnitedStates to John P. Bethke. No..-1,334,177, dated July 30 12, 1921,. or toJohn P. Bethke and R. H. Stearns. No. 1,407,051, dated. February 21,1922. Magnetic pulleys in which the windings are protected by sleeves orcoverings l2, composed of non-magnetic material, are 35 preferablyemployed since the apron is composed of magnetizable material, i. e.,steel, which provides a distribution of the lines of magnetieforcesimilar to that described in the above mentioned Patent No.1,407,051.

- polarity.

In a pulley'having a diameter of about 18 inches the pole pieces have. athickness of about two inches, which is about eight times the thicknessof the steel apron. Therefore, a small percentage of the lines ofmagnetic force will saturate the apron and the latter becomes magneticover substantially the entire area of that portion in proximity to thepulley without reducing the effective strength of the field beyond theapron. The abutting ends of the spools, composing the magnetic pulley,constitute annular pole pieces, and the spools are so wound that thesuccessive pole pieces will be of opposite It.w1ll be observed that theexciting windings 13 of the magnetic pulley are wholly protected by thespools 14 and the coverings 12, but that the pulley is well ventilated,the spools being spaced from the shaft and from each other to form anannular ventilating passage 15 and cavities 16 extending between thespools. The sprocket wheels are of skeleton, formation with openings 17to allow free circulation of air through the pulley. These sprocketwheels also carry the load of the apronand the material thereon, therebyrelieving the magnetic pulley from strain and making it possible towholly support the spools from the skeleton end walls 18 of the pulley.The pulley, however, is preferably splined atQOto the shaft 10, wherebyfriction'is avoided if any portion of the apron should come in contactwith its periphery. This makes it possible to bring the pulley intoextremely close proximity to the apron, i. e., into substantial contactwith it without subjecting the pulley to material pressure and withoutdeveloping friction if actual cont-act results.

Theoperation of apron feeders is slow and it'is customary to feedmaterial to the apron in irregular masses or piles, thus forming upontheapron a layer of material of varying thickness, and frequently of athickness or depth of one foot or more. But notwithstandingthe'thickness of this layer which would ordinarily make magneticseparation difficult, if not impossible, it has been found that theinvention above described can be utilized owing to the cascading ofthe'material across the delivery end of the conveyor,

i. e., over the magnetic pulley, whereby the material forms a thin layerover the surface of the pulley along that portion of the apron extendingdownwardly from a vertical plane through the axis of the pulley to ahorizontal. plane which includes such axis. The material not onlycascades in the form of a thin layer but thecomponent parts of the layeralso separate longitudinally as the motion of the falling bodiesaccelerates.

It is,

therefore, possible to rovide the apron feeder with stationary sidewalls or guards '24 to allow; the material to accumulate on the apron toa considerable depth throughout the width of the apron.

Referring now to Figures 3 and *1, it will be observed that in place ofthe magnetic employ a battery of electromagnetic spools 27, Q8, and 29connected by a yoke 30. Each spool has its core provided with anextended segmental pole piece 31, and the successive spools in the setor battery are oppositely wound, the pole pieces being thereby ofopposite polarity. The shaft 1.0 ofthe apron conveyor extends throughapertures in these pole pieces 31, whereby the shaft co-o ieratcs with anon-magnetic bar 32 in supporting the battery of magnets. The yoke 30rests upon the bar 32 as shown.

The curved surfaces 35 of the pole pieces 31 lie in an arc concentricwith the shaft to and in close proximity to the a pron. In thisconstruction it is, of course, desirable to prevent contact betweenthe'lnembers or plates 1, composing the apron and the pole'pieces.Therefore, the magnetic pulley disclosed in Figures 1 and 2 ispreferred. It is also preferred for the reason that its structureprovided for a more effective distribution of magnetic energy for thereasonsabove stated.

While I have described the apronsections 1 as being formed of steel, itwill be understood that any rigid material suitable for feeding heavymasses of rock or ore may be employed. Steelis preferably used for thereason above stated,'i. e., that it becomes magnetic in the vicinity ofthe pulley, and, therefore, more effective in holding magnetizablematerial. It also distributes the lines of magnetic force wherebymagnetizable material midway between the pole pieces may be attracteddirectly toward the apron along a line substantially perpendicular toits surface.

Because of difliculties incident to a path of low reluctance presentedby a conveyor of m'agnetizable material, rubber, leather, canvas andother fabric have been proposed but no substantial commercial successhas followed their use, largely because of lack of permanency andstability, whereas, with the present invention, the conveyor apron ofmetal, usually but not necessarily magnetizable, passes through themagnetic field in such a way as to afford a substantial and sufficientfield beyond the exposed face of the apron to effectively separate thema netizable from the non-magnctizablc mate rial of the load. Rotationof the magnetic pulley causes the magnetic held to trawl, with the loadand apron, and. where an apron of magnetizable mah'ria'l is used. the

l. in

the apron; so that a comparatively small resistance for a device of thiskind is offered I to the travel of the apron past the magnet.

Thus also relatively little current is'required for effectivelyenergizing the magnet, and a corresponding minimum of power used fordriving the apron, so that relatively small expense is involved inoperation and in original construction. Easily worn parts, multiplicityof magnets, wasteful distribution of magnetic fields, and high powerrequirements, have and will inevitably result in commercial failures.The present invention avoids all such, and enables attainment of maximumresults with a minimum outlay.

I claim:

1. An apron feeder having an endless con- \vyor apron.composed of aflexibly formed belt of substantially rigid sections of magnetizahlematerial, in combination with a magnet, the field of which includes thede-- magnet, the field of which includes the de livery end of theconveyor.

4. The combination of an apron feeder having a magnet-izable loadengaging and load-conveyor belt, and a revolving magnet located to haveits field influence the load through the belt.

The combination of an apron feeder having a conveyor apron composed oflapping metallic sections, and a rotary ma net located to have its fieldinfluence the load of the apron.

6. An apron feeder having an endless, metallic load-conveyor aproncomprising flexibly connected sections, in combination with a magnetmounted for having its field move with the load at one .place in thetravel of the apron for influencing magnetizable content of such load.

7 An apron feeder having an endless metallic conveyor apron comprising aload carrying reach and a return reach with bights between the reaches,in combination with a revolving magnet mounted between the reaches.

8. An apron feeder having an endless metallic conveyor apron comprisinga load carrying reach and a return reach with bights between thereaches, in combination with a magnet revolvably mounted in the bight ofFiedapron to have its field travel with the 9. An apron feeder having anendless conveyor apron composed of flexibly connected its periphery inclose proximity to the apron,

said pulley having annular pole pieces of successively oppositepolarity, said supporting wheels being adapted to su port the conveyorapron independently 0 said pulley, whereby to relieve said pulley fromthe weight of material being carried by said apron.

11. The combination with an electromagnethaving pole pieces of oppositepolarit of a feeding apron having supporting whee s for supporting saidapron independently of said pole pieces to revolve at its delivery endabout said pole pieces, each pole piece having a curved facesubstantially in an arc concentric 'with that along which the aprontravels.

12. The combination with an electromagnetic pulley having annular polepieces of successively opposite polarity, and a feeding apron havingsupporting wheels supporting said apron independently of said polepieces to travel at its delivery end about the axis of the ulley.

13. The combination with an electromagnetic pulley having anular polepieces of successively opposite polarity, a feeding apron. independentlysupported to travel at its delivery end about the axis of the pulley,and means for ventilating the pulley.

14. The combination with an electromagnetic pulley having a series ofannular magnetic windings and intervening pole pieces of oppositepolarity, and a covering for the windings composed of magnetizablematerial, of an apron feeder comprising a series of flexibly joinedmagnetizable members, means for supporting said feeder for travel aboutthe pu ley in close proximity thereto, said supporting means beingadapted to relieve the pulley from weight.

15. The combination with an electromag netic pulley having annular polepieces of opposite polarity, and intervening spacers of magnetizablematerial, forming, with the pole pieces, a' continuous cylinder, of anendless conveyor apron arranged to travel over and an electro-magneticpulley interposed between the wheels at the dehvery end of the conveyor,said plates being supported in their travel about-the pulley in closeproxim ity thereto.

17. The combination of an apifon feeder ha vini an endless conveyorcomprising magnetlza 1e plates each havmg arcuate marins transversely ofthe conveyor and interapped with the margins of adjacent plates, said(Flates being each hingedly secured to its a pu11ey at the delivery end.of the conveyor.

In testimony whereof, I have hereunto signed my name to thisspecification.

" JOHN P. BETHKE.

acent plates, and an electro-magnetie

